1. Field of the Invention
The present invention relates to a scheme for wire line data transmission in a mobile communication system which can reduce wire line transmission data between a plurality o base stations and a composition station during a soft handover in a mobile communication system based on CDMA (Code Division Multiple Access) scheme, and a base station apparatus and a mobile station apparatus suitable for this scheme for wire line data transmission.
2. Description of the Background Art
In the soft handover in a mobile communication system based on CDMA scheme, as shown in FIGS. 1A and 1B, a plurality of base stations 81 and 82 are connected with a mobile station 83 on one hand, and with a composition station 84 on the other hand. For an upward transmission, as indicated in FIG. 1A, upward transmission signals duplicated at the mobile station 83 are transmitted to the composition station 84 via radio transmission paths 85 and 86, base stations 81 and 82, and wire line transmission paths 87 and 88, and then composed at the composition station 84 and transmitted to an upper level station therefrom. For a downward transmission, as indicated in FIG. 1B, downward transmission signals duplicated at the composition station 84 are transmitted to the mobile station 83 via wire line transmission paths 89 and 90, base stations 81 and 82, and radio transmission paths 91 and 92, and then composed at the mobile station 83.
Note that, for the upward radio transmission from the mobile station 83 to the base stations 81 and 82, it is possible to use either a method for transmitting separate radio channels for a plurality of base stations 81 and 82 from the mobile station 83, or a method for transmitting only a single radio channel to be received by a plurality of base stations 81 and 82 from the mobile station 83. Also, a number of base stations for carrying out the soft handover is not necessarily limited to two, and three or more base stations may be involved in the soft handover.
In the soft handover described above, a plurality of base stations are connected with the composition station through a plurality of wire line transmission paths, and as shown in FIG. 2, signals for multiple channels are transmitted through each wire line transmission path, so that there has been a problem of a high wire line transmission cost.